Filter arrangement and methods

ABSTRACT

A filter arrangement includes a first filter element having opposite first and second ends; an axial length between the first and second ends; and a plurality of flutes. Each of the flutes has a first end portion adjacent to the first filter element first end, and a second end portion adjacent to the first filter element second end. Selected ones of the flutes are open at the first end potion and closed at the second end portion; and selected ones of the flutes are closed at the first end portion and open at the second end portion. A sleeve member secured to and circumscribing the first filter element. The sleeve member is oriented relative the first filter element to extend at least 30% of the axial length of the first filter element. A seal member pressure flange at least partially circumscribes the sleeve member. The filter arrangement is particularly useful for gas turbine systems. Methods for operating and servicing filter arrangements preferably utilize constructions herein.

TECHNICAL FIELD

[0001] This disclosure describes filter constructions for filteringfluids, such as gas or liquid. In particular, this disclosure describesa filter element, a pre-filter, a housing, and methods particularlyuseful with gas turbine systems.

BACKGROUND

[0002] Gas turbine systems are useful in generating electricity. Thesetypes of systems are particularly convenient in that they can beconstructed quickly; they are also desirable because they produce fewerharmful emissions than coal or oil based turbine systems. Gas turbinesutilize air for combustion purposes. Due to the precision moving partsin these types of systems, the combustion air needs to be clean. Toensure clean air for combustion, air filters have been used to clean theair taken into the gas turbine system. In prior art systems, a series ofpanel filters have been used to clean intake air. As systems became moresophisticated, cleaner air was required. This caused an increase incost.

[0003] Improvements in cleaning air intake into gas turbine systems isdesirable.

SUMMARY OF THE DISCLOSURE

[0004] In one aspect, the disclosure describes a filter arrangement. Ingeneral, the filter arrangement includes a first filter element havingopposite first and second ends; an axial length between the first andsecond ends; and a plurality of flutes. Each of the flutes has a firstend portion adjacent to the first filter element first end, and a secondend portion adjacent to the first filter element second end. Selectedones of the flutes are open at the first end portion and closed at thesecond end portion; and selected ones of the flutes are closed at thefirst end portion and open at the second end portion. A sleeve member issecured to and circumscribes the first filter element. The sleeve memberis oriented relative the first filter element to extend at least 30% ofthe axial length of the first filter element. A seal member pressureflange at least partially circumscribes the sleeve member.

[0005] In another aspect, a filtration system is described including atube sheet having at least a single through hole; a sleeve memberremovably and replaceably mounted in the hole; a flange at leastpartially circumscribing the sleeve member; a seal member compressedbetween and against the flange and the tube sheet; and a first filterelement secured within the sleeve member. The first filter elementpreferably is a straight flow through system comprising fluted media.

[0006] A prefilter element is also described. Preferably, the prefilterelement is removably mounted upstream of a primary filter element withina sleeve member. Methods of assembling the prefilter are described.

[0007] Systems for using preferred filter arrangements are described.Particularly useful systems include gas turbine systems.

[0008] Another aspect includes methods for operating and servicing.Preferred methods include constructions configured according toprinciples described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 is a schematic view of one embodiment of an air intakesystem for a gas turbine system having air filter arrangementsconstructed according to principles disclosed herein.

[0010]FIG. 2 is a schematic, front elevational view of one embodiment anair filter arrangement installed within a tube sheet, the primary filterelement being visible.

[0011]FIG. 3 is a schematic, rear elevational view of the air filterarrangement depicted in FIG. 2, the pre-filter element being visible.

[0012]FIG. 4 is a schematic, side elevational view of the air filterarrangement of FIGS. 2 and 3 installed in the tube sheet.

[0013]FIG. 5 is a schematic, fragmented, enlarged, cross-sectional viewof the air filter arrangement of FIGS. 2-4, taken along the line 5-5 ofFIG. 3.

[0014]FIG. 6 is a schematic, enlarged, top plan view of one embodimentof a latch utilized to hold the air filter arrangement of FIGS. 2-4 inthe tube sheet.

[0015]FIG. 7 is a schematic, perspective view of the air filterarrangement of FIGS. 2-4 and removed from the tube sheet, the primaryfilter element being visible.

[0016]FIG. 8 is a schematic, front elevational view of the air filterarrangement of FIG. 7, the primary filter element being visible.

[0017]FIG. 9 is a top plan view of the air filter arrangement of FIGS. 7and 8.

[0018]FIG. 10 is a schematic, exploded, enlarged perspective view of aclip and a sleeve for holding the filter elements utilized in the airfilter arrangement of FIGS. 2-4 and 7-9.

[0019]FIG. 11 is a schematic, top plan view of one embodiment of apre-filter utilized in the air filter arrangements of FIGS. 2-4 and 7-9.

[0020]FIG. 12 is a schematic, side elevational view of the prefilter ofFIG. 11.

[0021]FIG. 13 is a schematic, bottom plan view of the prefilter of FIGS.11 and 12.

[0022]FIG. 14 is a schematic, top plan view of another embodiment of aprefilter utilized in the air filter arrangements of FIGS. 2-4 and 7-9,during assembly.

[0023]FIG. 15 is a schematic, top plan view of another step ofassembling the prefilter of FIG. 14.

[0024]FIG. 16 is a schematic, perspective view of one embodiment of aportion of filter media usable in the primary filter element depicted inFIGS. 2, 7 and 8.

DETAILED DESCRIPTION

[0025] A. FIG. 1. System of Use

[0026] The air cleaner arrangements and constructions disclosed hereinare usable in a variety of systems. FIG. 1 depicts one particularsystem, in this case, a gas turbine system schematically at 20.

[0027] In FIG. 1, airflow is shown drawn into an air intake system 22 atarrows 23. The air intake system 22 includes a plurality of air filterarrangements 24 generally held in a tube sheet 36. In preferred systems,the tube sheet 36 will be constructed to hold the filter arrangements 24at an angle, relative to a vertical axis. Preferred angles will bebetween 5-25°, for example, about 7°. This permits liquid to drain fromthe filter arrangements 24 when the system 20 is not operating.

[0028] The air is cleaned in the air filter arrangements 24, and then itflows downstream at arrows 26 into gas turbine generator 28, where it isused to generate power.

[0029] B. Overview of Air Filter Arrangement

[0030] One example of an air filter arrangement 24 usable in system 20is shown in FIGS. 2-4. In general, the air filter arrangement 24includes a first, or primary filter element 30 and a second filterelement 32, which acts as a prefilter. By the term “prefilter”, it ismeant a separator that is positioned upstream of the main, primaryfilter element 30, that functions to remove large particles from the gasstream. The primary filter element 30 is viewable in FIG. 2, while theprefilter 32 is viewable in FIG. 3. The primary filter element 30 andthe prefilter element 32 are preferably secured within a sleeve member34 that is removably mountable in an aperture 38 in tube sheet 36. Ingeneral, air flow is taken in through the air intake system 22 and flowsfirst through the prefilter element 32 and then through the primaryfilter element 30. After exiting the primary filter element 30, the airis directed into the generator 28.

[0031] C. The Primary Filter Element

[0032] In reference now to FIGS. 2, 5, and 7, the primary filter element30 is configured to permit straight through flow. By the term “straightthrough flow,” it is meant that the fluid flows directly through thefilter element 30, entering at an inlet face 40 and exiting at anoppositely disposed outlet face 42, wherein the direction of fluid flowentering the inlet face 40 is in the same direction of fluid flowexiting the outlet face 42. In FIG. 2, it should be understood that theoutlet face 42 is shown schematically. That is, only a portion of theface 42 is shown with flutes. It should be understood that, in typicalsystems, the entire face 42 will be fluted.

[0033] The filter element 30 has a first end 44 and an opposite, secondend 46. In the arrangement depicted in FIG. 2, the first end 44 willcorrespond to an upstream end inlet face 40, while the second end 46will correspond to a downstream end outlet face 42. The straight throughflow allows gas to flow into the first end 44 and exit the second end46, such that the direction of the air flow into the first end 44 is thesame direction of air flow that is exiting the second end 46. Straightthrough flow patterns can reduce the amount of turbulence in the gasflow.

[0034] Attention is directed to FIG. 16. FIG. 16 is a schematic,perspective view demonstrating the principles of operation of certainpreferred media usable in the primary filter element 30. In FIG. 16,filter media in the form of a fluted construction is generallydesignated at 50. Preferably, the fluted construction 50 includes: alayer 52 of corrugations having a plurality of flutes 54 and a facesheet 56. The FIG. 16 embodiment shows two sections of the face sheet at56A (depicted on top of the corrugated layer 52) and at 56B (depictedbelow the corrugated layer 52). Typically, the preferred flutedconstruction 50 will include the corrugated layer 52 secured to thebottom face sheet 56B. When using this fluted construction 50 in arolled construction, it typically will be wound around itself, such thatthe bottom face sheet 56B will cover the top of the corrugated layer 52.The face sheet 56 covering the top of the corrugated layer 52 isdepicted as 56A. It should be understood that the face sheet 56A and 56Bare the same sheet 56.

[0035] When using this type of fluted construction 50, the flutechambers 58 preferably form alternating peaks 60 and troughs 62. Thetroughs 62 and peaks 60 divide the flutes into a two rows, one beingpositioned adjacent to (in FIG. 16 over or on top of) the other row. Inthe particular configuration shown in FIG. 16, the upper flutes formflute chambers 64 closed at the downstream end, while flute chambers 66having their upstream ends closed form the lower row of flutes. Thefluted chambers 66 are closed by a first end bead 68 that fills aportion of the upstream end of the flute between the fluting sheet 52and the second facing sheet 56B. Similarly, a second end bead 70 closesthe downstream end of alternating flutes 64.

[0036] When using media constructed in the form of fluted construction50, during use, unfiltered fluid, such as air, enters the flute chambers64 as indicated by the shaded arrows 72. The flute chambers 64 havetheir upstream ends 74 open. The unfiltered fluid flow is not permittedto pass through the downstream ends 76 of the flute chambers 64 becausetheir downstream ends 76 are closed by the second end bead 70.Therefore, the fluid is forced to proceed through the fluting sheet 52or face sheet 56. As the unfiltered fluid passes through the flutingsheet 52 or face sheet 56, the fluid is cleaned or filtered. The cleanedfluid is indicated by the unshaded arrow 78. The fluid then passesthrough the flute chambers 66, which have their upstream ends 80 closedto flow through the open downstream ends out the fluted construction 50.With the configuration shown, the unfiltered fluid can flow through thefluted sheet 52, the upper facing sheet 56A, or the lower facing sheet56B and into a flute chamber 66.

[0037] The fluted construction 50 is typically wound into a rolled orcoiled form, such as shown in FIG. 7. A variety of ways can be used tocoil or roll the fluted construction 50. The fluted construction 50 maybe wrapped around a central core; alternatively, the fluted construction50 may be coreless. Referring again to FIGS. 2, 7, and 8, note thecross-sectional shape of the filter element 30 is generally circular.The cross-section also could be non-circular, in other embodiments, suchas obround or “racetrack shaped.” By “obround” or “racetrack shaped,” itis meant that a filter element would define a curved (in someembodiments, semicircular) end and an opposite curved (in someembodiments, semicircular) end. The curved ends would be joined by apair of straight segments.

[0038] The media 50 can be a polyester synthetic media, a media madefrom cellulose, or blends of these types of materials. One example ofusable cellulose media is: a basis weight of about 45-55 lbs./3000 ft²(84.7 g/m²), for example, 48-54 lbs./3000 ft²; a thickness of about0.005-0.015 in, for example about 0.010 in. (0.25 mm); frazierpermeability of about 20-25 ft/min, for example, about 22 ft/min (6.7m/min); pore size of about 55-65 microns, for example, about 62 microns;wet tensile strength of at least about 7 lbs/in, for example, 8.5lbs./in (3.9 kg/in); burst strength wet off of the machine of about15-25 psi, for example, about 23 psi (159 kPa). The cellulose media canbe treated with fine fiber, for example, fibers having a size (diameter)of 5 microns or less, and in some instances, submicron. A variety ofmethods can be utilized for application of the fine fiber to the media,if it is desired to use fine fiber. Some such approaches arecharacterized, for example, in U.S. Pat. No. 5,423,892, column 32, atlines 48-60. More specifically, such methods are described in U.S. Pat.Nos. 3,878,014; 3,676,242; 3,841,953; and 3,849,241, incorporated hereinby reference. An alternative is a trade secret approach comprising afine polymeric fiber web positioned over conventional media, practicedunder trade secret by Donaldson Company under the designationULTRA-WEB®. With respect to the configurations of the filter element, ifit is desired to use fine fiber, there is no particular preference for:how the fine fibers are made; and, what particular method is used toapply the fine fibers. Enough fine fiber typically would be applieduntil the resulting media construction would have the followingproperties: initial efficiency of 99.5% average, with no individual testbelow 90%, tested according to SAE J726C, using SAE fine dust; and anoverall efficiency of 99.98% average, according to SAE J726C.

[0039] Example of usable filter constructions are described in U.S. Pat.No. 5,820,646, which patent is incorporated by reference herein.

[0040] D. The Prefilter Element

[0041] Attention is directed to FIGS. 3 and 11-13. The prefilter element32 is illustrated. Preferably, the prefilter element 32 is a pleatedconstruction 90 comprising a plurality of individual pleats 92. Thepleats 92 are arranged in a zig-zag fashion. As can be seen in FIGS. 3,11, and 13, preferred prefilter elements 32 will have a generallycircular cross-section.

[0042] The prefilter element 32 is configured to permit straight throughflow. In other words, the air flows directly through the prefilterelement 32, entering at an inlet face 94 and exiting at an oppositelydisposed outlet face 96, wherein the direction of fluid flow enteringthe inlet face 94 is in the same direction of fluid flow exiting theoutlet face 96.

[0043] In certain preferred embodiments, there will be at least 15pleats 92, no greater than 80 pleats 92, and typically 30-50 pleats 92.The pleated construction 90 is made from a media 98 that is folded inthe form of pleats 92 centered around a central core 100. Useable typesof media 98 includes fiberglass, or alternatively, an air laid media.Specific properties of usable media 98 include: a dry laid filter mediummade from polyester fibers randomly oriented to form a web having aweight of 2.7-3.3 oz./yd³ (92-112 g/m³); a free thickness (i.e.,thickness at 0.002 psi compression) of 0.25-0.40 in. (6.4-10.2 mm); anda permeability of at least 400 ft./min (122 m/min).

[0044] Preferred prefilter elements 32 will include a filter support orliner 102, at least on the downstream side 96. The filter support orliner 102 can be constructed of an expanded mesh, made from plastic ormetal. It should be noted that the liner 102 is illustratedschematically in FIG. 11. FIG. 11 shows the liner 102 only over acertain portion of the outlet face 96. This is to represent that theliner 102 covers the entire outlet face 96. In certain alternativeembodiments, the inlet face 94 can also have a filter support or liner.

[0045] Still in reference to FIG. 11, in the prefilter element 32illustrated, there is an adhesive 104 utilized to maintain the prefilterelement 32 in the shape of a circular pleated construction 90. Inparticular, the sealant 104 can be a bead 106 of hot-melt that isapplied to the pleated construction 90 after being shaped into acircular configuration. The bead 106 solidifies and helps to hold thepleated construction 90 in its circular configuration.

[0046] In general, the prefilter element 32 is removably and replaceablymountable in the sleeve member 34. The sleeve member 34 is described infurther detail below. In certain systems, the prefilter element 32 isheld within the sleeve member 34 by squeezing or compressing the endtips 108 of the media 98 against the inside wall of the sleeve member34. In other words, the primary filter element 32 is preferablyconstructed to have an initial, free-state, outermost dimension (in thiscase, diameter) that is greater than the inside diameter of the sleevemember 34. When placed inside of the sleeve member 34, the end tips 108of the media 98 are squeezed, compressed, bent, or smashed between theinside wall of the sleeve member 34 and the end of the liner 102.

[0047] An alternative embodiment of a prefilter element is illustratedin FIGS. 14 and 15, generally at 120. The prefilter element 120 isanalogous to prefilter element 32, in that it comprises a pleatedconstruction 122 of individual pleats 124. The prefilter element 120 isassembled differently from the prefilter element 32. In this embodiment,the prefilter element 120 is constructed by folding a sheet of media 126into a series of pleats 124. This forms a generally rectangular sheet128 of pleated media. The sheet 128 is inserted into a mold containingpolyurethane. The polyurethane is cured, to form a solid, rectangularend 130 of compressible polyurethane. This panel 132 can then beassembled into the prefilter element 120.

[0048] Attention is directed to FIG. 15. FIG. 15 illustrates the stepsof assembling the panel 132 into the prefilter element 120. The end 130is pinched together to form a core 134. End pleats 136, 138 are thenmoved toward each other in the direction of arrows 140, 142. In thismanner, the pleated panel 132 is fanned to form the circular prefilterelement 120. The end pleats 136 and 138 are then joined together with aclip.

[0049] The prefilter element 120 is convenient, in that the prefilterelement 120 can be stored and shipped to the end user in the form ofpanel 132. Just before installation, the panel 132 can be fanned out toform the resulting circular prefilter element 120.

[0050] E. The Sleeve Member and Clamping System

[0051] Preferred filter arrangements 24 constructed according toprinciples herein will have sleeve member 34 secured to andcircumscribing the primary filter element 30.

[0052] In general, the sleeve member 34 functions to hold the primaryelement 30 in place in the air intake system 22. Preferred sleevemembers 34 will also hold the prefilter element 32 in place upstream ofthe primary element 30.

[0053] Attention is directed to FIGS. 7-9. One preferred sleeve member34 is illustrated, holding the primary element 30. As can be seen inFIGS. 7 and 8, the sleeve member 34 preferably has a cross-section thatmatches the cross-section of the primary filter element. In this case,the primary filter element 30 has a generally circular cross-section;therefore, the preferred sleeve member 34 has a generally circularcross-section. It should be understood that in other embodiments, theprimary element 30 may have a cross-section of a different shape. Inthose cases, the sleeve member 34 would have a cross-section that wouldmatch the cross-section of the filter element 30.

[0054] As can be seen in FIG. 5, the sleeve member 34 includes asurrounding wall 150 that is curved in a form to result in a surroundingring 152. The wall 150 has a length that generally extends from the end153 (which, in this case, is even with second end 46 or outlet face 42of the primary element 30) to an opposite end 154. The sleeve member 34is preferably oriented relative to the primary filter element 30 toextend at least 30% of the axial length of the primary filter element30. In many typical arrangements, the sleeve member 34 will extendgreater than 50% of the axial length of the primary filter element 30.Indeed, in most preferred arrangements, the sleeve member 34 will extendat least the entire length (that is, 100%) of the axial length of theprimary filter element 30. In many typical applications, the sleevemember 34 will have a radius of at least 10 inches, typically 15-30inches, and in some instances, no greater than 50 inches.

[0055] The sleeve member 34 is preferably constructed and arranged witha sealing system to allow for securing the primary filter element 30 tothe tube sheet 36, without permitting unintended amounts of air frombypassing the primary element 30. In the arrangement depicted in FIGS.3, 5, and 7-9, the sleeve member 34 includes a seal member pressureflange 160. The flange 160 at least partially, and in most preferredembodiments, fully circumscribes the wall 150 of the sleeve member 34.Indeed, in most preferred embodiments, the flange 160 is extruded withthe wall 150 as a single extrusion 151, and then curved into a shapethat matches the cross-sectional configuration of the primary element30. The seal member pressure flange 160 operates as a backstop tosupport a seal member 162 in order to create a seal 164 between andagainst the flange 160 and the tube sheet 36. Preferably, the flange 160extends radially from the wall 150 of the sleeve member 34 and fullycircumscribes the seal member 34. The flange 160 will extend radiallyfrom the wall 150 a distance sufficient to support the seal member 162.In general, this distance will be at least 0.1 inches, typically 0.25-2inches, and in some embodiments may extend no greater than 10 inches.

[0056] As mentioned above, preferably, the flange 160 and the remainingportions of the sleeve member 34 are extruded as a single piece ofmaterial. In many applications, it is convenient to extrude the sleevemember 34 and flange 160 from plastic, such as high impact polystyrene.After extruding, the wall 150 with extending flange 160 is cut to thedesired length. The wall 150 with extending flange 160 is bent into acurved shape in order to support the primary filter element 30. Thebending can be accomplished by a cold rolling process. The ends 166, 168of the extrusion 151 are not, at this stage, joined together.

[0057] Attention is directed to FIG. 10. FIG. 10 shows the wall 150 withabutting ends 166, 168. Before the ends 166, 168 of the extrusion 151are pushed together, the primary filter element 30 is installed withinthe sleeve member 34. In some applications, the primary element 30 hasadhesive applied to its outer wall; alternatively, adhesive is appliedalong the inner surface of the wall 150; alternatively, adhesive isapplied to both the outer surface of the primary element 30 and theinner surface of the wall 150. The primary element 30 is then positionedinside of the aperture 170 formed by the sleeve member 34. A clampingmachine then presses the end 166 and the end 168 toward each other inabutting engagement to form joint 174. A patch or retaining clip 172 isthen placed over the joint 174 to secure the sleeve member 34 in itsfinal configuration (in the example shown in the FIGS., a generallycircular configuration). Preferably, the retaining clip 172 is securedin a permanent way to the sleeve member 34. For example, the retainingclip 172 may be secured to the wall 150 by ultrasonic welding.

[0058] Note that the retaining clip 172 is configured to overlap thejoint 174 completely between end 153 and end 154. That is, the clip 172has an end 176 that is generally flush or even with end 153. The cliphas an end 178 that is generally flush or even with end 154. The clip172 also has a protrusion 180 between the ends 176, 178 that overlapsand engages the flange 160. Preferred shapes of the protrusion 180 willbe something that defines an inside pocket 182 in the negative shape ofthe flange 160. In the embodiment illustrated in FIG. 10, the protrusion180 is U-shaped.

[0059] Attention is directed to FIG. 5. It can be seen that the flange160 includes first and second opposite axial sides 190, 192. One of theaxial sides, in this case side 190, supports the seal member 162. Theseal member 162 generally comprises a circular gasket 194. The gasket194 is preferably secured to the flange 160, by adhesive between thegasket 194 and the side 190 of the flange 160. The gasket 194 ispositioned on the flange 160, such that the gasket 194 completelycircumscribes the wall 150 and the primary element 30.

[0060] The arrangement depicted also includes a system for clamping thesleeve member 34 to the tube sheet 36. In the embodiment illustrated inFIGS. 3, 5, and 6, the clamping system includes a plurality of latchesor clamps 200. There should be enough latches or clamps 200 to form agood, tight seal 164 between the flange 160 and the tube sheet 36, whenthe sleeve member 34 is operably installed in the tube sheet 36. In theembodiment shown in FIG. 3, there are 4 clamps 200. Each of the clamps200 is evenly spaced radially along the periphery of the flange 160. Inother embodiments, there can be more than 4 clamps 200 for example, 6-10clamps. In certain other embodiments, there can be fewer than 4 clamps200.

[0061] Attention is directed to FIGS. 5 and 6. In FIG. 5, the clamp 200is shown in cross-section. Each of the clamps 200 includes a lever 202,a nose 204, and a plate 206. The plate 206 includes apertures 208, 210for accommodating a fastener, such as a bolt 212 to secure the clamp 200to the tube sheet 36.

[0062] The nose 204 operates to apply pressure to the flange 160 andcompress the seal member 162 against the tube sheet 36. The lever 202operates to selectively move the nose 204 toward and away from the tubesheet 36. For example, when installing the filter arrangement 34 in thetube sheet 36, the lever 202 may be depressed by a person's thumb orhand to move the nose 204 in a direction away from the tube sheet 36.This allows the system installer to manipulate the filter arrangement 24in a way that the flange 160 can be positioned between the nose 204 andthe tube sheet 36. In other embodiments, the clamps 200 can behand-tightened, such as using wing nuts.

[0063] F. Methods

[0064] In operation, the filter arrangement 24 is used as follows. Airto be filtered in the system 20 is directed at arrows 23 into the intakesystem 22. The air first flows through the prefilter element 32. The airenters at the inlet face 94, passes through the media 126, and exitsthrough the outlet face 96. The prefilter element 32 removes largerparticles and debris from the intake air. Next, the air enters theprimary filter element 30. The air enters at the inlet face 40, passesthrough the fluted construction 50, and exits at the outlet face 42.From there, the air is taken into the generator 28.

[0065] In typical operation, there is an overall pressure drop acrossthe filter arrangement 24 of about 0.6-1.6 inches of water. Thisincludes both the primary filter element 30 and the prefilter 32.Typically, the pressure drop across the prefilter 32 alone will be about0.2-0.6 inches of water, while the pressure drop across the primaryelement 30 alone will be about 0.4-1 inch of water.

[0066] After a period of operation, the filter arrangement 24 should beserviced. It may be that the prefilter element 32, 120 will require moreservicing (i.e., removal and replacement) than the primary element 30.To service the prefilter element 32, 120 the prefilter element 32, 120is grasped at its pleats 92, 124 and removed from the sleeve member 34.This can be done by pulling the prefilter element 32, 120 fromfrictional engagement with the inner surface of the wall 150. The oldprefilter element 32, 120 may then be disposed of. A second, newprefilter element 32, 120 is provided. The prefilter element 120 may bein the form of panel 132; alternatively, the prefilter element 32 may bein the form of the pre-made circular prefilter 32. The panel 132 ismanipulated, such that the individual pleats 124 are fanned out, and endpleat 136 is joined to the end pleat 138. Typically, end pleat 136 isthen clipped or joined to end pleat 138, to form the circular prefilterelement 120. The new prefilter element 32, 120 is then placed inside ofthe sleeve member 34. This may be done by radially compressing the endtips 108 of the pleated media against the inner surface of the wall 150.This frictional engagement helps to hold prefilter element 32, 120 inplace. It should be noted that the pressure of the system 20 also helpsto hold the prefilter element 32, 120 in place in the sleeve member 4.

[0067] From time to time, the primary element 30 will also requireservicing. Typically, this will be after a pressure drop of about 3-4inches of water. To service the primary element 30, the sleeve member 34is removed from the tube sheet 36. This is done by breaking the seal 164between the flange 160 and the tube sheet 36. To break the seal 164,each of the clamps 200 may need to have each of its levers 202depressed, such that the nose 204 is moved away from the tube sheet 36.The sleeve member 34 is then slid axially from the tube sheet 36 alongthe aperture 38 defined by the tube sheet 36.

[0068] The primary element 30 along with the sleeve member 34 may thenbe disposed of. Preferably, the primary element and sleeve member 34 areconstructed completely of non-metallic materials, such that they can bereadily incinerated. Preferably, the primary element 30 and sleevemember 34 are at least 95%, more typically at least 99% non-metallic.Alternatively, the primary element 30 may be removed from the sleevemember 34, and the sleeve member 34 may be reused.

[0069] A second, new sleeve member 34 with a new primary element 30 isthen provided. The sleeve member 34 holding the primary filter element30 is axially placed inside of the aperture 38 of the tube sheet 36.Each of the clamps 200 is manipulated by depressing the lever 200 inorder to permit the flange 160 to be placed between the nose 204 and thewall of the tube sheet 36. This places the seal member 162 between andagainst the flange 160 and the tube sheet 36 to create seal 164. Aprefilter element 32, 120 may then be installed in the sleeve member 34.

[0070] The above specification, examples, and data provide a completedescription of the manufacture and use of the invention. Manyembodiments of the invention can be made.

We claim:
 1. A filter arrangement comprising: (a) a first filter elementhaving opposite first and second ends; an axial length between saidfirst and second ends; and a plurality of flutes; (i) each of saidflutes having a first end portion adjacent to said first filter elementfirst end, and a second end portion adjacent to said first filterelement second end; (A) selected ones of said flutes being open at saidfirst end portion and closed at said second end portion; and selectedones of said flutes being closed at said first end portion and open atsaid second end portion; (b) a sleeve member secured to andcircumscribing said first filter element; (i) said sleeve member beingoriented relative said first filter element to extend at least 30% ofsaid axial length of said first filter element; and (c) a seal memberpressure flange at least partially circumscribing said first filterelement.
 2. A filter arrangement according to claim 1 wherein: (a) saidseal member pressure flange extends radially from said sleeve member andfully circumscribes said sleeve member.
 3. A filter arrangementaccording to claim 2 wherein: (a) said seal member pressure flange isintegral with said sleeve member.
 4. A filter arrangement according toclaim 2 wherein: (a) said sleeve member includes a surrounding wall; and(b) said seal member pressure flange and said surrounding wall are asingle, extruded piece.
 5. A filter arrangement according to claim 4wherein: (a) said sleeve member has a circular cross-section with adiameter of at least 20 inches.
 6. A filter arrangement according toclaim 2 further comprising: (a) a seal member secured to a portion ofsaid seal member pressure flange.
 7. A filter arrangement according toclaim 6 wherein: (a) said seal member pressure flange includes first andsecond opposite axial surfaces; and (b) said seal member is secured tosaid first axial surface and circumscribes said sleeve member.
 8. Afilter arrangement according to claim 2 wherein: (a) said sleeve memberincludes: (i) a wall with first and second opposite, abutting ends; and(ii) a retaining clip securing together said first and second abuttingends.
 9. A filter arrangement according to claim 1 further including:(a) a second filter element adjacent to said first filter element; saidsecond filter element being circumscribed by said sleeve member.
 10. Afilter arrangement according to claim 9 wherein: (a) said second filterelement is removable and replaceable from said sleeve member.
 11. Afiltration system comprising: (a) a tube sheet having at least a singlethrough hole; (b) a sleeve member removably and replaceably mountedthrough said hole; (c) a flange at least partially circumscribing saidsleeve member; (d) a seal member pressed between and against said flangeand said tube sheet; and (e) a first filter element secured within saidsleeve member and through said hole; said first filter element havingopposite first and second ends; and a plurality of flutes; (i) each ofsaid flutes having a first end portion adjacent to said first filterelement first end, and a second end portion adjacent to said firstfilter element second end; (A) selected ones of said flutes being openat said first end portion and closed at said second end portion; andselected ones of said flutes being closed at said first end portion andopen at said second end portion.
 12. A filtration system according toclaim 11 further comprising: (a) a clamping system to provide axialpressure on said flange to press said seal member between said flangeand said tube sheet.
 13. A filtration system according to claim 12wherein: (a) said clamping system includes a plurality of springsmounted on said tube sheet.
 14. A filtration system according to claim11 further comprising: (a) a second filter element removably andreplaceably mounted in said sleeve member adjacent to said first filterelement first end.
 15. A filtration system according to claim 14wherein: (a) said second filter element comprises pleated media.
 16. Afiltration system according to claim 11 wherein: (a) said tube sheetcomprises a plurality of through holes; and wherein the system furtherincludes: (b) a sleeve member removably and replaceably mounted in eachof the through holes of the tube sheet; each of the sleeve membershaving a flange circumscribing a respective sleeve member; (c) a flutedfilter element mounted in each of the sleeve members; (d) a seal memberbeing compressed between each of the flanges and the tube sheet; and (e)a pleated filter element mounted in each of the sleeve members andadjacent to a respective fluted filter element.
 17. A method ofservicing an air filtration system for a gas turbine system; the methodcomprising: (a) removing a prefilter element from a sleeve member; thesleeve member being mounted through a hole in a tube sheet; and (b)replacing the pre-filter with a second pre-filter by compressing ends ofmedia of the second pre-filter against an inner wall of the sleevemember.
 18. A method according to claim 17 wherein: (a) said step ofreplacing the pre-filter includes: (i) providing the second pre-filteras a pleated panel; and (ii) fanning the pleated panel to form acircular, pleated pre-filter.
 19. A method according to claim 17 furtherincluding: (a) removing the sleeve member holding a primary filterelement from the tube sheet; (i) the primary filter element includingopposite upstream and downstream ends; the primary filter element havinga plurality flutes, each of the flutes having a first end portionadjacent to the filter element upstream end, and a second end portionadjacent to the filter element downstream end; selected ones of theflutes being open at the first end portions and closed at the second endportions, and selected ones of the flutes being closed at the first endportions and open at the second end portions.
 20. A method according toclaim 19 wherein: (a) said step of removing a sleeve member includesbreaking a seal between the sleeve member and the tube sheet.